This invention relates generally to solid-state lasers and, more particularly, to solid-state blue-green lasers, which operate at wavelengths between approximately 450 nanometers (0.45 microns) and 580 nm (0.58 microns).
Blue-green lasers have been proposed for use as a communications link between orbiting satellites and underwater submarines. The blue-green region of the electromagnetic spectrum is of interest because attenuation of light through sea water is minimized at the blue-green wavelengths. A submarine communications link would include an array of blue-green lasers positioned on each of a number of orbiting satellites to provide complete coverage of the earth's oceans and a very sensitive detection device placed onboard each submarine to receive the very faint laser signals.
The submarine detection device would require a solar filter, such as an atomic resonance filter, to remove background solar radiation which otherwise would prevent detection of the laser signals. An atomic resonance filter provides filtering by absorbing light at one wavelength and then reradiating the energy at another wavelength. The reradiated energy is then detected by some type of photodetector, such as a photomultiplier tube. One particular type of atomic resonance filter uses elemental cesium in vapor form and has absorption lines in the blue region of the electromagnetic spectrum at wavelengths of 455.6 nm (0.4556 microns) and 459.3 nm (0.4593 microns).
Although an atomic resonance filter provides extremely sharp filtering capabilities, the large distances involved between an orbiting satellite and an underwater submarine require that highly efficient lasers with relatively high power outputs be used. Solid-state lasers are preferred for satellite applications because of their small size and light weight. Although solid-state lasers have been designed that operate at wavelengths matching the absorption lines of cesium, these lasers are typically complex, not highly efficient and have relatively low power outputs. Accordingly, there exists a need for a simple, highly-efficient solid-state laser with relatively high power outputs that operates at a wavelength matching one of the absorption lines of cesium. The present invention clearly fulfills this need.